Semiconductor device and method of manufacturing semiconductor device

ABSTRACT

Disclosed is a semiconductor device comprising a substrate, an insulating film formed above the substrate and containing a metal, Si, N and O, the insulating film containing metal-N bonds larger than the sum total of metal-metal bonds and metal-Si bonds, and an electrode formed above the insulating film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityfrom U.S. Application Ser. No. 10/772,280, filed Feb. 6, 2004 and isbased upon and claims the benefit of priority from the prior JapanesePatent Application No. 2003-031466, filed February 7, 2003, the entirecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and a method formanufacturing the same, and more particularly, to a semiconductor devicecontaining an insulating film having a high dielectric constant, and amethod for manufacturing the same.

2. Description of the Related Art

Recently, as the next generation gate insulator replacing an silicondioxide film (SiO₂ film), expectations for high dielectric films such asmetal silicate films including an Hf silicate film (HfSiO film) haveincreased. Since the dielectric constant of the Hf silicate film ishigher than that of an SiO₂ film, the equivalent oxide thickness (EOT)of the Hf silicate film can be reduced while keeping sufficient physicalthickness to suppress leakage current.

To form an effectively thin gate insulator, the dielectric constant ofthe film is desirably as high as possible. Such a dielectric film can beattained by increasing the amount of Hf in the film. However, anexcessively large amount of Hf is reported to cause phase separation andcrystallization of a film, increasing leakage current.

To prevent the crystallization, use of an HfSiON film formed by adding Nto an HfSiO film has been proposed (M. R. Visocay et al., Appli. Phys.Lett., 80, 3183 (2002)). According to the proposal, it is confirmed thatwhen an HfSiO film and HfSiON film are heat-treated for 60 seconds in anN₂ atmosphere, the HfSiO film is crystallized at 1,000° C., whereas theHfSiO film remains in amorphous even at 1100° C.

However, as a result of our investigation, we have found that since anHf—N bond is not present in the films formed by conventional methods, itis not easy to increase the concentrations of both Hf and N.

Therefore, the ratio (percentage) of Hf/(Hf+Si) of a conventional HfSiONfilm remains at most about 44%. Therefore, an HfSiON film having a highdielectric constant capable of suppressing crystallinity and leakagecurrent has not yet been realized.

It has been confirmed that the HfSiON film formed by an on-axissputtering method contains Hf—N bonds in an amount of less than 1%.Therefore, an HfSiON film containing a large amount of Hf cannot beobtained.

As described, it has been difficult to form an HfSiON film having a highdielectric constant, capable of suppressing crystallinity and leakagecurrent.

Under the circumstances, the present invention is directed to providinga semiconductor device having an insulating film formed of anitrogen-incorporated metal silicate film with a high dielectricconstant, capable of reducing leakage current lower than an oxide film,and suppressing crystallinity and also directed to the method formanufacturing such a semiconductor device.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided asemiconductor device comprising: a substrate; an insulating film formedabove the substrate and containing a metal, Si, N and O, the insulatingfilm containing metal-N bonds larger than the sum total of metal-metalbonds and metal-Si bonds; and an electrode formed above the insulatingfilm.

According to another aspect of the present invention, there is provideda semiconductor device comprising: a substrate; an insulating filmformed above the substrate and containing a metal, Si, N and O, theinsulating film being amorphous and containing a metal-N bond; and anelectrode formed above the insulating film.

According to another aspect of the present invention, there is provideda method for manufacturing a semiconductor device comprising: forming aninsulating film containing a metal, Si, N and O, above a substrate by anoff axis sputtering method, the insulating film containing metal-N bondslarger than the sum total of metal-metal bonds and metal-Si bonds; andforming an electrode above the insulating film.

According to another aspect of the present invention, there is provideda method for manufacturing a semiconductor device comprising: forming anitride film having a off-stoichiometric composition containing a metaland Si above a substrate by an off-axis sputtering method; oxidizing thenitride film to form an insulating film containing metal-N bonds largerthan the sum total of metal-metal bonds and metal-Si bonds; and formingan electrode above the insulating film.

According to another aspect of the present invention, there is provideda method for manufacturing a semiconductor device comprising: forming anoxide film having a off-stoichiometric composition containing a metaland Si above a substrate by an off-axis sputtering method; nitriding theoxide film to form an insulating film containing metal-N bonds largerthan the sum total of metal-metal bonds and metal-Si bonds; and formingan electrode above the insulating film.

According to another aspect of the present invention, there is provideda method for manufacturing a semiconductor device comprising forming ametal silicide film having a off-stoichiometric composition containing ametal and Si above a substrate by an off-axis sputtering method;oxynitriding the metal silicide film to form an insulating filmcontaining metal-N bonds larger than the sum total of metal-metal bondsand metal-Si bonds; and forming an electrode on the insulating film.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a graph showing the X-ray photoelectron spectroscopy (XPS)measurement results, that is, an Hf4f spectrum of an HfSiON film,according to one embodiment of the present invention;

FIG. 2 is a graph showing the XPS measurement results, that is, an Si2pspectrum of the HfSiON film according to one embodiment of the presentinvention;

FIG. 3 is a graph showing the relationship between equivalent oxidethickness (EOT) of an HfSiON film and Jg where Vg=Vfb−1(V);

FIG. 4 is a graph showing the relationship between the oxygen atomicpercentage (O_(at)) and nitrogen atomic percentage (N_(at)) of an HfSiONfilm;

FIG. 5 is a graph showing a band gap of an HfSiON film;

FIG. 6 is a graph showing the relationship between voltage and leakagecurrent;

FIG. 7 is a graph showing an in-plane x-ray diffraction (XRD) pattern ofan HfSiON film according to one embodiment of the present invention;

FIG. 8 is a transmission electron microscope (TEM) image showing asectional view of an HfSiON film after heat treatment;

FIG. 9 is a TEM image showing a crosssection view of another HfSiON filmafter heat treatment; and

FIG. 10 is a sectional view of a semiconductor device according to oneembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be explained with reference tothe accompanying drawings.

As the results of intensive studies, the present inventors found thatthe leakage current increases when the both Hf and N concentrations of aconventional HfSiON film are simply increased for the reasons mentionedbelow.

The conventional HfSiON film is an insulator containing Si—N bonds, Si—Obonds, and Hf—O bonds. The composition is represented by the followingformula.(HfO₂)_(x)(SiO₂)_(y)(Si₃N₄)_(1-x-y)where 0<x<1 and 0<y<1

Since N binds only to Si, when the concentration of N increases, theconcentration of Si inevitably increases whereas the concentration of Hfdecreases. Conversely, when the Hf concentration increases, theconcentration of N decreases. In an attempt to increase both Hf and Nconcentrations of the HfSiON film, Hf—Hf bonds and Hf—Si bonds arenaturally contained in addition to the Si—N bonds, Si—O bonds, and Hf—Obonds. However, because of the Hf—Hf bonds and the Hf—Si bonds beingmetallic bonds, when both Hf and N concentrations simply increase in aconventional HfSiON film, leakage current occurs.

When Hf—N bonds are present in an HfSiON film in addition to Si—N bonds,Si—O bonds, and Hf—O bonds, the composition of the film is expressed bythe following formula:((SiO₂)_(1-x)(Si₃N₄)_(x))_(1-z)((HfO₂)_(1-y)(HfN_(α))_(y))_(z)where 0<x, y, z<1, α= 4/3

In the HfSiON film having the aforementioned composition, theconcentrations of Hf and N can be increased. In addition, it is foundthat Hf—N bonds, different from Hf—Hf bonds and Hf—Si bonds, do notincrease the leakage current if they are contained in the film. However,to obtain the effect of the Hf—N bonds, Hf—N bonds need to be presentlarger than the sum total of the Hf—Hf bonds and Hf—Si bonds. It is moredesirable that metallic bonds such as Hf—Hf bonds and Hf—Si bonds arenot substantially present.

As a result, the concentrations of Hf and N were successfully increasedwithout increasing the amount of leakage current, enabling the formationof a film having a high dielectric constant.

The HfSiON film containing a large number of Hf—N bonds can be formed byan off-axis sputtering method. In a general on-axis sputtering method, asputtering target is arranged at a position facing a substrate, whereas,in an off-axis sputtering method, the sputtering target is arranged at aposition not facing the substrate, more specifically, arranged at aposition perpendicular to the substrate. With this arrangement, it ispossible to prevent the invasion of highly accelerated ions and neutralatoms from a target into a film.

More specifically, in the on-axis sputtering method, the highlyaccelerated particles or ions enter a film almost at a right angleduring film formation. Before bonds are sufficiently formed, nextdeposition takes place. In contrast, in the off-axis sputtering method,particles or ions do not enter the film. As a result, nitrogen ions arediffused into a film surface and bonded to not only Si but also Hf,thereby obtaining Hf—N bonds.

Since the formulation and the bonding state of ions are influenced bythe difference in film formation mechanism, an HfSiON film containingHf—N bonds can be formed by the off-axis sputtering method.

When forming an HfSiON film by the off-axis sputtering method, an HfSiONfilm can be formed directly on a substrate. To describe morespecifically, HfSiON film can be formed by sputtering anHfSi_(x)O_(y)N_(z) target (containing-Hf—N bonds in an amount of 1% ormore based on the total number of all bonds) in an Ar atmosphere or bysputtering an HfSi_(x) target (x>1) in an atmosphere containing Ar, N₂and O₂. Alternatively, the HfSiON film can be formed by sputtering, in apredetermined atmosphere, at least one target selected from Hf,.HfO_(x),Hf₃N₄ and HfN_(x) (x<2) in combination with at least one target selectedfrom Si, SiO_(x) (x<2) and SiN_(x) (x< 4/3). The conditions of thesputtering are not limited as long as it is an off-axis sputtering.

When an HfSiON film is treated with heat, it is desirable that anantioxidant film is formed on the HfSiON film in advance. It ispreferable that the antioxidant film is formed on the HfSiON filmcontinuously right after the formation of the HfSiON film by usingpoly-Si, poly-Ge or a metal. When a transistor is formed by using theHfSiON film as a gate insulator, the antioxidant film can be used as adummy gate, which thus may be removed after the heat treatment.

The HfSiON film may also be formed by depositing a nitride (HfSiN) filmhaving a off-stoichiometric composition by an off-axis sputteringmethod, followed by oxidizing it. The HfSiN film having aoff-stoichiometric composition can be oxidized by rapid thermalannealing (RTA), spike annealing at atmospheric pressure in an O₂ambient, plasma oxidation, or radical oxidation. Alternatively, theHfSiON film may be formed by depositing an HfSiO film having aoff-stoichiometric composition by an off-axis sputtering method,followed by nitriding it. Nitridation can be performed by rapid thermalnitridation (RTN), plasma nitridation, radical nitridation, or spikeannealing in N₂ atmosphere. Furthermore, the HfSiON film may be formedby depositing an HfSi film having a off-stoichiometric composition by anoff-axial sputtering method, followed by oxynitriding it. Theoxynitridation process may be performed by heat treatment in NO gas.

When the off-stoichiometric HfSiN film is formed, a target formed of,for example, HfSi_(x) or HfSiN may be used. Alternatively, sputteringmay be performed in a predetermined atmosphere by using a target formedof Hf or HfN in combination with a target formed of Si or SiN.

When a off-stoichiometric HfSiO film is formed, a target formed ofHfSi_(x) (x<1) or HfSi_(x)O_(y) (x<1 and y<2) may be used, oralternatively, a target made of Hf or HfO_(x) may be used in combinationwith a target of Si or SiO_(x) as a sputtering target.

In either case, the film having a off-stoichiometric composition need tobe formed by sputtering in order to make oxidation proceed easily andlower the oxidation temperature to suppress the oxidation of an Sisubstrate. After an HfSiON film is formed, heat treatment is performedin vacuum, O₂, N₂, H₂, or H₂/N₂ atmosphere at a temperature of 450 to1100° , thereby repairing defects in the film to increase the filmdensity. As a result leakage current can be suppressed and dielectricconstant can be increased.

When an HfSi film having a off-stoichiometric composition is formed, atarget formed of HfSi_(x)(x<1) may be used. Alternatively, sputteringcan be performed by using a target formed of Hf may be used incombination with a target formed of Si.

Now, an example in which an HfSiON film is formed by depositing an HfSiNfilm on a p-type Si (100) substrate by an off-axis sputtering method,followed by oxidizing the HfSiN film will be explained below.

A p-type Si (100) substrate was subjected to a common washing process(standard cleaning) performed with SC2 (HCl/H₂O₂/H₂O) and then to HFtreatment. Subsequently, the substrate was washed with running purewater, dried and introduced into an off-axis sputtering apparatus.

In an off-axis sputtering apparatus, Hf target and Si targets werepreviously arranged individually with right angles to a substrate to beused. Into the off-axis sputtering apparatus, a p-type Si (100)substrate was introduced, the Hf and Si targets were sputtered in an Aror N₂ atmosphere to obtain an HfSiN film having a off-stoichiometriccomposition.

The HfSiN film thus deposited was taken out in the air and thenintroduced into rapid thermal annealing (RTA) apparatus, in which RTAwas performed at atmospheric pressure in an O₂ ambient, thereby formingan HfSiON film. The HfSiON film thus obtained was measured by X-rayelectron spectroscopy (XPS) using. AXIS-ULTRA sold by Kratos Analyticalof Shimazu Group.

The obtained Hf4f spectrum is shown by a solid line in FIG. 1. Forcomparison, the Hf4f spectrum of an HfSiO film is shown by a brokenline. In the spectrum of FIG. 1, the peaks of about 19.7 eV and 18.0 eVof the broken line exhibited the presence of Hf—O bonds. Since peaks ofthe solid line were present at points on slightly lower energy side ofthe peaks of the broken line, the presence of Hf—N bonds in the HfSiONfilm was identified. The fact that there were no peaks at about 13 eVand 15 eV clearly demonstrates that metallic bonds (Hf—Si bonds andHf—Hf bonds) were not substantially present in the HfSiON film.

Since the detection limit of XPS is 1%, it was found that theconcentration of the Hf—N bonds was 1% or more by molecular percentage.To suppress the crystallization of an HfSiON film, the concentration ofHf—N bonds must be 1% or more.

Furthermore, Rutherford Backscattering Spectroscopy (RBS) measurementdemonstrated that the ratio of Hf/(Hf+Si) in the HfSiON film is about47%. Since Hf—N bonds were formed, Hf was contained in a larger amountthan a conventional case. As described, Hf—N bonds need to be containedin 1 atomic % or more and the ratio of Hf/(Hf+Si) is about 47%. Due tothe ratio of Hf/(Hf+Si) being 47%, the HfSiON film has a dielectricconstant of 15 or more. This is confirmed based on measurement ofcapacitance.

The Si2p spectrum of the same whole HfSiON film obtained by XPSmeasurement is shown in FIG. 2. In FIG. 2, the peak at about 103 eVrevealed the presence of Si—O bonds. The peak at about 102 eV (at thelower energy side than 103 eV) revealed the presence of Si—N bonds.There was no peak at about 98 to 100 eV. This fact clearly demonstratesthat no metallic bond (Si—Si bonds and Hf—Si bonds) substantiallyexisted.

From the results of FIGS. 1 and 2, it was demonstrated that Hf—O, Si—O,Si—N, and Hf—N bonds are present in the HfSiON film. RBS measurementrevealed that the content of N is 28.5 atomic % or more. The resultmeasured by the XPS usually show content of each bonds of whole film.

Those spectrum peak of each bond may change depending onmetal/(metal+Si) ratio of the film, therefore the position of bindingenergy of each bond in the film may be determined based on themetal/(metal+Si) ratio of the film and positions of binding energies ofHf—O bond and Si—O bond of the film having the metal/(metal+Si) ratio.

The spectrum peaks may also be measured by Energy Dispersive X-rayFluorescence Spectrometer (EDX) or by Electron Energy Loss Spectroscopy(EELS).

The graph of FIG. 3, shows the relationship between the equivalent oxidethickness (EOT) of an HfSiON film and the leakage current density Jg atVg=Vfb−1 (V) where Vg is a gate voltage and Vfb is a flat band voltage.The graph also shows trend lines for an SiO₂ film and a conventionalHfSiON film (indicated as Ref.) based on the results previouslyreported.

From the graph of FIG. 3, leakage current (Jg) tends to increase as EOTdecreases. The leakage current (Jg) is lower than that of SiO₂ by notless than four orders of magnitude and lower than the conventionalHfSiON film (Ref.) by about two orders of magnitude. This is considereddue to the ratio of Hf/(Hf+Si) of the conventional HfSiON film (Ref.)being as low as about 40%. In particular, the leakage current from theHfSiON film having about 0.6 nm thick (in terms of EOT) was reduced byabout five orders of magnitude compared to that of the SiO₂ film.

It has not been identified that Hf—N bonds are present in a conventionalHfSiON film formed by an on-axis sputtering method. To confirm this, anHfSiON film was formed by an on-axis sputtering method in the samemanner as described above except that Si and Hf targets were arranged atthe positions facing a substrate.

The HfSiON film thus obtained was subjected to XPS measurement. As aresult, Hf—N bonds were not detected but detected a large number ofmetallic bonds such as Hf—Hf bonds and Hf—Si bonds. At this time, theratio of Hf/(Hf+Si) in the HfSiON film was about 39% and the content ofN was about 25 atomic %. Since the ratio of Hf/(Hf+Si) is about 39%, thedielectric constant of the HfSiON film remains about 13.

As described, in the HfSiON film having no Hf—N bonds, large leakagecurrent is generated due to the presence of a large number of metallicbonds, and crystallization occurs due to insufficient N content.Furthermore, the dielectric constant is limited due to in sufficient Hfcontent.

Since the HfSiON film of the embodiment of the present invention doesnot substantially contain metallic bonds but contain Hf—N bonds, Hf andN are contained in considerably large amounts compared to a conventionalHfSiON film. Therefore, it becomes possible to increase a dielectricconstant, suppress crystallization and reduce leakage current.

The graph of FIG. 4 shows the relationship between oxygen atomic percent(O_(at)) and nitrogen atomic percent (N_(at)) in the HfSiON films. As isshown in the figure, although the HfSiON films differ in ratio ofHf/(Hf+Si), the oxygen atomic ratio and the nitrogen atomic ratio areapproximately distributed along a straight line. In other words,(O_(at)) and (N_(at)) satisfy the relationship represented by formula(1) below:2(O_(at))+3(N_(at))=4((Si_(at))+(Hf_(at)))   (1)with the proviso that (O_(at)) and (N_(at)) satisfy the relationshiprepresented by formula (2) below:(O_(at))+(N_(at))+(Si_(at))+(Hf_(at))=100   (2)

On the assumption that (Hf_(at)) is zero, this relationship satisfied by(O_(at)) and (N_(at)) will be equal to that of SiON film having astoichiometric composition. In the case of SiON film, Si having 4coordinations to N (3 coordinations) or O (2 coordinations). Therefore,if (Hf_(at)) is 0, the SiON film satisfies the condition represented bythe formula (1).

Hence, the SiON can be regarded as a pseudo-binary alloy (S. V.Hattangady et al., J. Vac. Sci. Technol. A14, 3017 (1996)) representedby formula (3).(SiO₂)_(x)(Si₃N₄)_(1-x)   (3)

From formula (1), the HfSiON film according to the embodiment of thepresent invention is considered as the same as stoichiometric SiON whoseSi is partially replaced with Hf. On the analogy of pseudo-binary alloymodel represented by formula (3) of an SiON film, the HfSiON film can beexpressed by a pseudo-quaternary alloy represented by formula (4) below:(HfO₂)_(x)(SiO₂)_(1-x))_(z)(Hf₃N₄)_(y)(Si₃N₄)_(1-y))_(1-z)   (4)where 0<x, y, z <1

In formula (4), x and y are variables expressing degrees of freedom of Oand N in preferentially binding to either Hf or Si.

If HfSiON is expressed by formula (4), Hf—N bonds have a nature of theshort-range order of Hf₃N₄. This is the point to be especially notified.It is well known that HfN is a metal. When HfN is a metal, Hf and N arepresent in the ratio of 1:1. However, When HfN is present in the ratioof Hf:N=3:4, that is, Hf₃N₄, is not a metal but an insulating material(B. O. Johnson et al., J. Mater. Res. 1, 442 (1986); P. Kroll, Phys.Rev. Lett. 90, 125, 501 (2003)).

On the assumption that the HfSiON film according to the embodiment ofthe present invention contains an alloy of Hf₁N₁, the HfSiON film shouldbe present at the lower side of Hf₃N₄ in FIG. 4. However, actually, theHfSiON film is distributed approximately along the line indicated byHf₃N₄ satisfying formula (4). From this fact, the Hf—N bonds containedin the HfSiON film may be said as the same dielectric bonds as Hf₃N₄.

Further note that, simply because Hf satisfies formula (4), it cannot besaid that Hf has the same four coordinations as Si. This is because thenumbers of valences of N and O may also change in accordance with Hf.More specifically, if Hf has X coordination (X is 4 to 8), O and N areset at X/2 coordination and 3X/4 coordination , respectively, there isno discrepancy in formula (4).

Next, the band gap Eg of an HfSiON film was examined by ReflectionElectron Energy Loss Spectroscopy (REELS). The results are shown in FIG.5. Since the ratio of Hf/(Hf+Si) is 80%, and a value (N_(at)) is as highas 20 and 35%, a large number of Hf—N bonds are present in the HfSiONfilm. When the Hf—N bond is a metallic bond, the band gap approximateszero. Actually, the band gap of the film is about 3 eV or more.Therefore, it was confirmed that the Hf—N bonds contained in an HfSiONfilm according to the present invention are not metallic bonds butdielectric bonds such as Hf₃N₄.

An HfSiON film according to the embodiment of the present invention maybe formed on a Si substrate via an interface layer. When the interfacelayer is formed substantially thin so as not to increase the substantialthickness of the entire structure, it is possible to enhance theperformance of a transistor. Furthermore, it is not always necessary forsuch an HfSiON film to have a uniform composition in the thicknessdirection. A larger number of Hf—N bonds may be present both surfaces ofthe HfSiON film. This case is favorable since the interface layer can bemade thinner.

Using the HfSiON film formed by the off-axis sputtering method asmentioned above, a structure composed of an Au electrode, an HfSiONfilm, and p-Si (100) was formed and its electric characteristics werechecked. The relationship between the leakage current and the voltage ofthe HfSiON film is shown in the graph of FIG. 6, in which curve “a”shows the results of the HfSiON film containing N in an amount of 52%,and the ratio of Hf/(Hf+Si) is 47%. For comparison, in FIG. 6, curve “b”indicates the relationship between the leakage current and the voltageof an SiO₂ film.

The HfSiON film and the SiO₂ film were formed with an effectivethickness of 2 nm. The term “effective thickness” refers to the electricthickness of the HfSiON film estimated by regarding the dielectricconstant of the SiO₂ film as 3.9. From the results shown in the graph ofFIG. 6, it is found that the current flowing the HfSiON film is lowerthan that of SiO₂ film by one to two orders of magnitude at all voltagevalues. When an electric field of 5 MV/cm is applied to the HfSiON film,the leakage current of the HfSiON film becomes lower than that of SiO₂film by two orders of magnitude.

As already explained in the above, in a conventional HfSiON filmcontaining no Hf—N bonds, it has been impossible to sufficientlyincrease its Hf concentration and reduce the leakage current. Incontrast, in the HfSiON film according to the embodiment of the presentinvention, since Hf—N bonds are contained larger than metallic bonds,the concentration of Hf can be increased. Therefore, leakage current canbe decreased while maintaining a high dielectric constant. Thisadvantage is achieved for the first time by the present invention.

Similarly, the state of the HfSiON film formed by an off-axis sputteringmethod was checked by in a plain x-ray diffraction (in plain XRD)method. The results are shown in FIG. 7. Since the XRD pattern shown inFIG. 7 shows no peak. This fact means that no crystallization occurs.From this, it is demonstrated that the crystallization of HfSiON film issuppressed. The HfSiON film remains in an amorphous state without beingcrystallized even after the heat treatment performed at a hightemperature of 1,000° C. or more.

FIGS. 8 and 9 show TEM images showing a crosssection of an HfSiON filmafter the heat treatment.

In the HfSiON film shown in FIG. 8, the ratio of Hf/(Hf+Si) is 55% and avalue of (Nat) is 38 atomic %. The film was treated with heat without anantioxidation film provided thereon. On the other hand, in the HfSiONfilm shown in FIG. 9, the ratio of Hf/(Hf+Si) is 60% and a value of(Nat) is 33 atomic %. The film was treated with heat with anantioxidation film provided thereon.

FIG. 8 shows a crystallized HfSiON film. An interface layer of about 5nm thick is observed between the Si substrate and the interface. Incontrast, FIG. 9 shows a non-crystallized HfSiON film. The interfacelayer formed between the Si substrate and the HfSiON film is up to about1 nm.

FIG. 10 shows a crosssection of an example of a semiconductor device, anMOS transistor, according to one embodiment of the present invention.The semiconductor device of embodiment of the present invention is notlimited to the MOS transistor and SOI and a vertical transistors may beused.

In the MOS transistor shown in the figure, the isolation region 60formed of a silicon thermal oxide is formed on a p-type siliconsubstrate 50, thereby forming the active region. A source/draindiffusion regions 70, 80 doped with phosphorus as an impurity areseparately formed. Note that the substrate is not limited to bulksilicon. Any substrate may be used as long as its channel region isformed of Si, Ge, SiGe or a compound semiconductor.

On the surface of the p-type silicon substrate 50 sandwiched by thesource and drain diffusion regions, a gate insulting film 90 of HfSiONis formed by the method mentioned above and further a gate electrode 180constituted by a polycrystalline silicon film is formed by a CVD method.On the gate electrode 180, a silicon oxide film 110 is formed by the CVDmethod. On the sidewall of the gate electrode 180, a silicon nitridefilm 120 is arranged. The gate electrode 180 may be formed of a metalsuch as TiN, Au, Al, Pt or Ag.

Impurities are activated by annealing to form the source and draindiffusion regions 70 and 80. The annealing is performed in an atmosphereof an inert gas such as N₂, Ar, or He, or vacuum.

Although it is not shown, the gate electrode 180 and the source/draindiffusion regions 70 and 80 may be overlapped with each other. In thiscase, in the overlapped region, a film such as an SiO₂, Si₃N₄ or SiONfilm having a lower dielectric constant than an HfSiON film may beformed.

On the isolation region 60 and silicon oxide film 110, the interlayerinsulating film 130 formed of a silicon oxide film is arranged. On thesource and drain diffusion region, an aluminum electrode 140 serving aswiring is formed via a silicide film 150. Such a structure is formed asfollows. A silicon oxide film is formed over the entire surface of thesubstrate 50 having the isolation region 60 and the silicon oxide film110 to form the interlayer insulating film 130. Subsequently, a contacthole is formed and then an aluminum film is deposited by sputtering,followed by patterning it.

The MOS transistor shown in FIG. 10 has a gate insulating film 90 formedof an HfSiON film containing Hf—N bonds in a larger amount than that ofmetallic bonds. Because of this, even if a high temperature process of1,000° C. or more is performed, the resultant MOS transistor showed goodoperation while the leakage current of the gate insulating film issuppressed low.

The HfSiON film containing Hf—N bonds larger than metallic bonds can beused as the insulating film between gate electrodes, a tunnel insulatingfilm of nonvolatile memory device and the gate insulating film of a CMOStransistor. In these cases, the same effects can be obtained.Furthermore, when the HfSiON film is used as a capacitor insulating filmof a capacitor, the substantial film thickness thereof can be reducedwhile suppressing the leakage current.

In the foregoing, a nitrogen-containing metal silicate film has beenexplained by way of an example of an HfSiON film. However, the presentinvention is not limited to the HfSiON film. The same discussion can beapplied to a ZrSiON film and the same effects can be obtained.Furthermore, when Hf is replaced with a lanthanoide series element suchas La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu, anitrogen-containing metal silicate film having the same effect can beobtained.

As explained in the foregoing, according to the present invention, it ispossible to provide a semiconductor device having an insulating filmformed of a nitrogen-containing metal silicate film which is capable ofsuppressing the crystallization of a film, having a sufficiently highdielectric constant, and reduced in leakage current lower than an oxidefilm, and further provide a method for manufacturing the semiconductordevice.

The present invention makes it possible to improve the reliability of asemiconductor device such as an MOS transistor and bring anextraordinary industrial value.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A semiconductor device comprising: a substrate; an insulating filmformed above the substrate and comprising Hf, Si, O and N, a content ofHf—N bonds being 1 atomic % or more; and an electrode formed above theinsulating film.
 2. The semiconductor device according to claim 1,wherein metallic bonds formed by Hf—Hf bonds and Hf—Si bonds are notsubstantially present.
 3. The semiconductor device according to claim 1,wherein a content of metallic bonds formed by Hf—Hf bonds and Hf—Sibonds are less than a detection limit.
 4. The semiconductor deviceaccording to claim 1, wherein a content of the N in the insulating filmis 28.5 atomic % to 52 atomic %.
 5. The semiconductor device accordingto claim 1, wherein a content of the Hf in the insulating film is 47atomic % or more based on the total amount of the Hf and Si.
 6. Thesemiconductor device according to claim 1, wherein a dielectric constantof the insulating film is 15 or more.
 7. The semiconductor deviceaccording to claim 1, wherein the insulating film is in an amorphousstate.
 8. The semiconductor device according to claim 1, wherein thesubstrate has impurity diffusion regions formed in separate regions ofthe substrate, the insulating film is a gate insulating film formedbetween the impurity diffusion regions, and the electrode is a gateelectrode.
 9. A semiconductor device comprising: a substrate; aninsulating film formed above the substrate and comprising Zr, Si, O andN, a content of Zr—N bonds being 1 atomic % or more; and an electrodeformed above the insulating film.
 10. The semiconductor device accordingto claim 9, wherein metallic bonds formed by Zr—Zr bonds and Zr—Si bondsare not substantially present.
 11. The semiconductor device according toclaim 9, wherein a content of metallic bonds formed by the Zr—Zr bondsand Zr—Si bonds are less than a detection limit.
 12. The semiconductordevice according to claim 9, wherein a content of the N in theinsulating film is 28.5 atomic % to 52 atomic %.
 13. The semiconductordevice according to claim 9, wherein a content of the Zr in theinsulating film is 47 atomic % or more based on the total amount of theZr and Si.
 14. The semiconductor device according to claim 9, wherein adielectric constant of the insulating film is 15 or more.
 15. Thesemiconductor device according to claim 9, wherein the insulating filmis in an amorphous state.
 16. The semiconductor device according toclaim 9, wherein the substrate has impurity diffusion regions formed inseparate regions of the substrate, the insulating film is a gateinsulating film formed between the impurity diffusion regions, and theelectrode is a gate electrode.